The present invention relates to a display device and a panel light source device, more particularly to a display device and a panel light source device, which have locating portions or engaging portions on a light guide plate and a frame.
As an image display device for various monitors for a personal computer and so on, a liquid crystal display device has been remarkably widespread. The liquid crystal display device generally has a liquid crystal display panel and a backlight unit disposed on at the rear thereof. The liquid crystal display panel performs an image display by controlling light transmitted therethrough. Among some types of liquid crystal display devices, there is one having a side light type backlight. This type of liquid crystal display device has a cathode fluorescent tube as a light source disposed on a side of a display surface for the purpose of thinning the liquid crystal display device.
FIG. 1 is a schematic view showing a liquid crystal display device 10 having a side light type backlight unit. In the drawing, a reference numeral 11 denotes a backlight unit, a numeral 12 a liquid crystal panel (liquid crystal cell), and a numeral 13 a diffusion sheet for diffusing light to make the brightness even on a liquid crystal display panel surface. A reference numeral 14 denotes a prism sheet for converging light to improve a luminance on the front surface of the display, reference numeral 15 is a light guide plate for guiding and diffusing light from a light source, and reference numeral 16 is a frame for accommodating parts of the backlight unit 11 such as the light guide plate and the prism sheet therein. A reference numeral 17 denotes a cold cathode tube 17 as a light source, reference numeral 18 is a bezel for holding and protecting the liquid crystal cell 12 and the backlight unit 11 from the outside thereof. The backlight unit 11 is made of the diffusion sheet 13, the prism sheet 14, the light guide plate 15, the frame 16 and the cold cathode tube 17. The cold cathode tube 17 is disposed inside the frame 16 and is not directly shown in the drawing.
In order to prevent a rattle or a positional shift of each part, it is necessary to locate and fix each part of the backlight unit 11 in the frame 16. Particularly, since the light guide plate 15 is thick in comparison with other optical parts, it is subject to be broken. Alternatively, the light guide plate 15 may sometimes destroy the cold cathode tube 17 by colliding with the cold cathode tube 17. Therefore, it is necessary to locate and fix the light guide plate 15 on the frame 16 accurately. A method for fixing the light guide plate 15 on the frame 16 is that convexities are provided on the light guide plate 15, opening portions are provided on the frame 16, and the convexities and the opening portions are engaged with each other to be located and fixed with each other. Optical sheets, such as the prism sheet 14 and the diffusion sheet 13, are attached to the light guide plate 15 by adhesive to be fixed thereto.
Techniques for forming convexities on a light guide plate and engaging them with holes of a frame as described above are described, for example, in the gazette of Japanese Patent Laid-Open No. Hei 9-152577. However, there have existed some problems in providing such convexities on a light guide plate. One problem is that the convexities are subject to be broken. The light guide plate is typically formed of acrylic resin. Since the strength of the acrylic resin is not high, the convexities sometimes may be chipped off. Due to difference of thermal expansion ratios between that of the light guide plate and that of the frame, the convexities are stressed, resulting in breakage thereof. Widening spaces between the convexities and the holes is conceived in order to prevent the breakage. However, such space widening causes a rattle between the frame and the light guide plate. Alternatively, also in the case where an impact is delivered to the backlight unit due to dropage and so on, the convexities sometimes may be broken.
On the other hand, in a portable computer or the like using a liquid crystal display device, enlargement of a display screen thereof has been required in recent years while the display device is being miniaturized. For this reason, a border portion of the display device has been made still narrower. This is generally called xe2x80x9cborder narrowingxe2x80x9d of the display device. The border portion is a portion between the display screen area and the end of the display device. According to such border narrowing, a width of the frame has been narrowed. Thus, it has come to be difficult for the holes for fitting the convexities of the light guide plate therein to be provided on the frame.
Against the above-described backlight unit, a backlight unit having convexities provided on a frame and locating holes formed by hollowing out a light guide plate is described, for example, in the gazette of Japanese Patent Laid-Open No. Hei 11-84351. The foregoing problems can be solved by providing the convexities on the frame. However, engaging portions where the convexities and the through holes are engaged cannot emit light. Accordingly, the engaging portions are formed onto the display area as a result of the border narrowing, thus causing a problem that a dark portion is formed on the display screen.
The object of the present invention is to solve the foregoing problems and so on.
One feature of the present invention is a panel light source device including a light source, a light guide plate for guiding and diffusing light from the light source, and a frame for housing the light guide plate, wherein the frame has a convexity inside thereof and the light guide plate has a concavity on a side or lower surface thereof, the convexity and the concavity are engaged with each other, and the light guide plate is provided in the frame so as to cover at least a part of an upper surface of the light guide plate.
In another feature of the present invention as a display device, such a display device that performs a display by controlling light projected from a backlight unit with a display panel, in which the backlight unit includes a light source, a light guide plate for guiding and diffusing light from the light source, and a frame for housing the light guide plate, wherein the frame has a convexity in an inside thereof, the light guide plate has a concavity on a side or lower surface thereof, the convexity and the concavity are engaged with each other, and the light guide plate is provided so as to cover at least a portion of an upper surface of the convexity in the frame.
Still another aspect of the present invention is a display device, which performs a display by controlling light projected from a backlight unit with a display panel, in which the backlight unit includes a light source, a light guide plate for guiding and diffusing light from the light source, and a frame for housing said light guide plate, wherein the frame has a convexity for locating the light guide plate thereon, the light guide plate has a concavity for engaging the convexity therewith, and light from the light source is projected from an upper surface of the concavity.
Various other objects, features, and attendant advantages of the present invention will become more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views.